Distinct Element Modelling of Masonry Wall Panels with Openings

Abstract

Cracking of the masonry walls of low-rise domestic and commercial buildings above windows and door openings often occurs as a result of a lack of support from a lintel or other similar structural member. Many thousands of low-rise domestic and commercial buildings in the UK are afflicted by these problems which are exacerbated by in-plane thermal and moisture movements as well as the effects of settlement and subsidence. The cost, time and effort associated with repairing such damage is usually significant from the owner's perspective, particularly when the disruption to the normal use of the building is taken into account. Therefore, it is important to gain an improved understanding of the behaviour of masonry wall panels with openings so that cost-effective, minimum disruption repair or strengthening techniques can be developed. The development of a reliable computational model is particularly important to avoid the need for costly, repetitive laboratory testing of large-scale wall panels. In the current research work, a two-dimensional distinct element modelling software package (UDEC) [1] has been used to predict the qualitative behaviour of a single leaf thick brick masonry wall panel with a 2m clear opening when subjected to a gradually increased vertical load. The results from UDEC were compared with the experimental results obtained from the full-scale testing of unreinforced brick masonry wall panels at the University of Bradford [2]. The experimental results showed that there were three notable features of the behaviour of the wall panels that occurred with increasing applied load. These consisted of initial flexural cracking followed by the propagation of diagonal stepped cracks from the corners of the opening leading, finally, to collapse. These three features were also predicted using the UDEC model. In particular, the model captured the tensile and shear failure of the brick/mortar interfaces as well as the collapse mode. Hence, it is concluded that a distinct element numerical model such as UDEC can be used successfully to predict the qualitative behaviour of a panel of brickwork containing a large opening when subjected to a gradually increased in-plane vertical load. The next stage of the research will be focused on improving the performance of the model so that a quantitative analysis can be performed. Different forms of strengthening will then be incorporated into the model which will be further validated using the results from full-scale laboratory testing of strengthened wall panels.